Pipe fixing structure and pipe fixing method

ABSTRACT

A pipe fixing structure and method are disclosed. In the pipe fixing structure, an ejector  1  on which a pipe  2  is to be fixed is subjected to a pressure which is exerted on the pipe  2  thereby to deform and fix the pipe  2 . An enlarged portion  1   a  larger than the outer diameter of the pipe 2, through which the pipe  2  can be inserted in axial direction, is formed in the ejector  1 . A thin portion  2   a  is formed on the inner peripheral portion of the pipe  2 , and a first projection  6  is formed by plastic deformation of the thin portion  2   a  of pipe  2  under the pressure. The first projection  6  coincides with the enlarged diameter portion  1   a  so that the pipe is fixed on the ejector  1.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a pipe fixing structure and a pipe fixingmethod for fixing a pipe onto an object member by plastically deformingthe pipe under an external force.

2. Description of the Related Art

The conventional pipe fixing structure and method in which a pipe isfixed by caulking on an object member to which the pipe is to be fixed(hereinafter referred to simply as “the object member”) is known. Noreference of the prior art is known to the inventor. This conventionalpipe fixing structure and method are described below.

As shown in FIG. 14, a projection 104 is formed at a predeterminedposition on an outer peripheral portion 105 of a pipe 100, and an objectmember 103 is formed with an opening portion 106 into which the pipe 100with the projection 104 can be inserted, a stopper portion 108 on theopening in contact with the forward end 107 of the pipe 100 and a holder101 extended from the opening portion 106.

As a method of fixing this pipe 100 on the object member 103, an O-ring102 is placed on the opening portion 106, the forward end 107 of thepipe 100 is brought into contact with the stopper portion 108 and theO-ring 102 is held by the lower side surface of the projection 104.Under this condition, the holder 101 is pushed down by a punch member(not shown). The holder 101 bends down and pushes the upper side surfaceof the projection 104 thereby to fix the pipe 100 on the object member103.

A method is also available in which the pipe is fixed on an object byplastically deforming the pipe to a predetermined shape. As such amethod, the conventional technique described in Japanese UnexaminedPatent Publication No. 2003-336560 is known. In this method, the forwardend of a pipe held in a chuck is pressed in the axial direction by apunch member having a predetermined shape of a depression. Then, themachining margin at the forward end of the pipe plastically flows sothat the forward end of the pipe is deformed into a shape following thepredetermined shape of the depression formed on the punch member.

SUMMARY OF THE INVENTION

In the conventional method of fixing by caulking, however, the holder101 is projected outward from the object member 103 and, therefore theobject member 103 is required to be cut or otherwise machined to formthe holder 101, thereby posing the problem that the object member beforemachining is bulky. Also, the machining process to form the holder 101projected outward requires a considerable amount and labor for thecutting work.

The object of this invention, which has been achieved in view of theproblem described above, is to provide a pipe fixing structure and apipe fixing method whereby at least a predetermined fixing force can besecured with a simple structure without forming the outward projectionof the object member.

In order to achieve the object described above, this invention employsthe following technical means.

According to a first aspect of the invention, there is provided a pipefixing structure for deforming and fixing a pipe (2) by applying a forceto press the pipe (2) in axial direction against an object member (1, 8)to which the pipe (2) is to be fixed, the pipe fixing structurecomprises an enlarged diameter portion (1 a) formed in the object member(1, 8), which portion (1 a) is larger than the outer diameter of thepipe (2) and through which the pipe (2) can be inserted in axialdirection, and a first projection (6) into the shape of which a thinportion (2 a) of the pipe (2) is deformed under the pressure, whereinthe first projection (6) coincides with the enlarged diameter portion (1a).

In this aspect of the invention, an enlarged diameter portion is formedin the object member, the pipe is formed with a thin portion, and theaxial pressure is applied to the pipe thereby to buckle and fix thepipe. Therefore, the fixing process can be simplified with a simplefixing structure and the pipe can be fixed with at least a predeterminedfixing force.

According to a second aspect of the invention, there is provided a pipefixing structure comprising a second projection (7, 15) projectedradially outward from the pipe (2) and integrated with the object (1, 8)in the boundary between the fixed pipe (2) and the outer surface of theobject member (1, 8). In this aspect of the invention, the expansion ofthe second projection further strengthens the fixing force between thepipe and object member.

According to a third aspect of the invention, there is provided a pipefixing structure wherein the second projection (15) is formed in asubstantially uniform thickness along the shape of the outer surface ofthe object member (1). In this aspect of the invention, the secondprojection is formed along the shape of the outer surface of the objectmember in the boundary between the pipe and the outer surface of theobject member. Therefore, the coupling portion is less visible and burrsor the like edge portions of the second projection can be reduced.

According to a fourth aspect of the invention, there is provided a pipefixing structure wherein the cross section of the enlarged diameterportion (1 a) in axial direction of the pipe (2) is progressivelyreduced outward. In this aspect of the invention, the cross section ofthe enlarged diameter portion in axial direction of the pipe isprogressively reduced outward. Therefore, the first projection of thepipe plastically flows in close contact with the progressively reducedshape. Thus, the gap between the object member and the pipe is reducedto increase the closeness and the fixing force.

According to a fifth aspect of the invention, there is provided a pipefixing structure wherein the object member is an ejector for therefrigeration cycle.

According to a sixth aspect of the invention, there is provided a pipefixing method comprising the steps of forming a thin portion (2 a) onthe inner peripheral portion of the pipe (2), forming the enlargeddiameter portion (1 a), at a position corresponding to the thin portion(2 a), through which the pipe (2) can be axially inserted, in the objectmember (1, 8) to which the pipe (2) is fixed, and inserting the pipe (2)into the object member (1, 8) and pressing the pipe (2) in axialdirection so that the thin portion (2 a) is deformed by being projectedoutward into coincidence with the enlarged diameter portion (1 a).

In this aspect of the invention, after the comparatively simple processof forming a thin portion of the pipe and an enlarged diameter portionin the object member, the pipe is axially pressed and buckled. Thus, apipe fixing method high in workability, buckling process quality andfixing force is realized.

According to a seventh aspect of the invention, there is provided a pipefixing method wherein the pipe (2) inserted into the object member (1,8) is pressed in axial direction in such a manner that the outerperipheral portion of the pipe (2) is gripped by a chuck (3, 13), andthe chuck (3, 13) is moved in axial direction. In this aspect of theinvention, the pressure exerted on the pipe can be adjusted easily bymoving the chuck mechanically in axial direction. Therefore, a fixingmethod is obtained in which the deformation amount of the thin portionand the closeness between the thin portion and the enlarged diameterportion can be easily adjusted.

According to an eighth aspect of the invention, there is provided a pipefixing method comprising the step of deforming the thin portion (2 a)into coincidence with the enlarged diameter portion (1 a), followed byapplying pressure to the pipe (2) thereby to buckle the pipe (2) in theboundary between the fixed pipe (2) and the outer surface of the objectmember (1, 8).

In this aspect of the invention, the second projection expanding outwardis formed by buckling the pipe in the boundary between the fixed pipeand the outer surface of the object member, thereby furtherstrengthening the fixing force between the pipe and the object member.

According to a ninth aspect of the invention, there is provided a pipefixing method wherein the chuck (3, 13) moved in axial direction whilegripping the outer peripheral portion of the pipe (2) has, on the sidethereof for gripping the pipe (2), an end surface (14) in opposedrelation to the outer surface of the object member (1, 8), which endsurface (14) is formed along the shape of the outer surface of theobject member (1, 8).

In this aspect of the invention, burrs or the like edges are preventedfrom being formed in the boundary between the pipe and the outer surfaceof the object member in the buckling step, on the one hand, and thebuckled portion of the pipe can be formed to the desired thickness, onthe other hand.

According to a tenth aspect of the invention, there is provided a pipefixing method wherein the outer surface of the object member (1) iscurved, and the object member (1, 8) side end surface (14) of the chuck(13) near to the object member (1, 8) for gripping the pipe (2) iscurved or inclined along the shape of the curved outer surface of theobject member. In this aspect of the invention, a pipe fixing method isobtained in which the boundary between the pipe and the outer surface ofthe object member can be formed in the shape having a greater similarityto the curved surface of the object member.

According to a 11th aspect of the invention, there is provided a pipefixing method comprising the step of inserting the pipe (2) into theobject member (1, 8) and thus pressing the pipe (2) in axial directionwith a support member (5) inserted in the pipe (2), whereby the thinportion (2 a) is deformed to form an outward projection coincident withthe enlarged diameter portion (1 a).

In this aspect of the invention, the pipe is pressed and rendered toflow plastically with the support member inserted in the pipe, andtherefore the pipe is urged with a stronger force to expand outward atthe time of plastic flow, thereby making it possible to deform the pipeinto the more desired shape.

According to an 12th aspect of the invention, there is provided a pipefixing method comprising the step of forming, in the object member towhich the pipe (11) is to be fixed, an insertion opening into which thepipe (11) can be inserted and forming an enlarged diameter portion (1 a)larger than the insertion opening and the outer diameter of the pipe(11) in the object member (1), and the step of applying the axialpressure only to the pipe (11) and deforming by projecting the outerperipheral portion of the pipe (11) outward into coincidence with theenlarged diameter portion (1 a) while inserting the pipe into the objectmember (1) from the insertion opening and holding the outer surface ofthe pipe (11).

In this aspect of the invention, a pipe fixing method is obtained inwhich at least a predetermined fixing force can be secured by a simpleprocess not including the step of forming the object member into theshape projected outward.

The reference numerals in the parentheses attached to the names of therespective means represent the correspondence with the specific means,respectively, included in the embodiments described later.

The present invention may be more fully understood from the descriptionof preferred embodiments of the invention, as set forth below, togetherwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing an automotive refrigeration cycleusing an ejector to which the pipe fixing structure and the pipe fixingmethod according to a first embodiment are applicable.

FIG. 2 is a schematic diagram showing a configuration of the ejector towhich the pipe fixing structure and the pipe fixing method according tothe first embodiment are applicable.

FIG. 3 is a sectional view showing the state before the pipe is pressedin the pipe fixing method according to the first embodiment.

FIG. 4 is a sectional view showing the state before the pipe is pressedfor fixing the pipe in the axial direction of the object member in thepipe fixing method according to the first embodiment.

FIG. 5 is a sectional view showing the state in which the pipe isinserted into the object member from the state before fixing the pipe inFIG. 3.

FIG. 6 is a sectional view showing the state after forming the firstprojection from the state of FIG. 5 in the pipe fixing method accordingto the first embodiment.

FIG. 7 is a sectional view showing the state after forming the secondprojection from the state of FIG. 6.

FIG. 8 is a perspective view showing the second projection in the pipefixing structure according to the first embodiment.

FIG. 9 is a sectional view showing the state before the pipe is pressedin the pipe fixing method according to the second embodiment.

FIG. 10 is a sectional view showing the state after forming the firstprojection from the state of FIG. 9.

FIG. 11 is a sectional view showing the state before forming the secondprojection in the pipe fixing structure and method according a thirdembodiment.

FIG. 12 is a sectional view showing the state after forming the secondprojection from the state of FIG. 11.

FIG. 13 is a perspective view showing the second projection in the pipefixing structure according to the third embodiment.

FIG. 14 is a sectional view showing the conventional pipe fixingstructure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

The pipe fixing structure and the pipe fixing method according to thefirst embodiment of the invention are used to fix a pipe on a metaldevice constituting an object member through which a fluid flows. As anexample, an explanation is made for a case in which a pipe is fixed onan ejector used for the refrigeration cycle. First, the configuration ofthe ejector and the configuration of the refrigeration cycle using theejector are explained.

FIG. 1 is a schematic diagram showing the automotive refrigeration cycleusing the ejector to which the pipe fixing structure and the pipe fixingmethod according to this embodiment are applicable.

The refrigeration cycle including the ejector has a refrigerantcirculation path 11 in which the refrigerant circulates, and acompressor 12 for sucking in and compressing the refrigerant is arrangedin the refrigerant circulation path 11.

This compressor 12 is adapted to be rotationally driven through a beltor the like by a vehicle driving engine (not shown). The compressor 12is a variable replacement refrigerant compressor capable of adjustingthe refrigerant discharge ability with the change in discharge capacity.The discharge capacity corresponds to the refrigerant amount dischargedper rotation and can be changed by changing the refrigerant intakevolume.

The variable displacement refrigerant compressor 12 is typically ofswash plate type, in which specifically, the piston stroke is changed bychanging the angle of the swash plate and thus the refrigerant intakevolume is changed. The angle of the swash plate can be electricallycontrolled from an external unit by an electromagnetic pressure controlunit 12 a making up a capacity control mechanism to change the pressure(control pressure) of the swash plate chamber.

A radiator 13 is arranged downstream of the compressor 12 in therefrigerant flow. The radiator 13 cools the high-pressure refrigerant byexchanging heat between the high-pressure refrigerant discharged fromthe compressor 12 and the atmospheric air (outdoor air) blown in by acooling fan (not shown).

An ejector 14 is arranged further downstream of the radiator 13 in therefrigerant flow. The ejector 14 constitutes a decompression means forreducing the pressure of the fluid on the one hand and a kinetic vacuumpump for transporting the fluid by the suction effect of the workingfluid ejected at high speed at the same time.

FIG. 2 is a schematic diagram showing a configuration of the ejector towhich the pipe fixing structure and the pipe fixing method according tothis embodiment are applicable.

The ejector 14 includes a nozzle portion 14 a having a small path areafor reducing the refrigerant flowing in from the radiator 13 and anintake portion 14 c arranged in the same space as the refrigerantejection port of the nozzle portion 14 a for sucking in the gas-phaserefrigerant from a second evaporator 18 described later.

A needle valve 14 e for controlling the opening degree of the ejectionport is arranged on the same axis as the ejection port in the nozzleportion 14 a in a manner movably by an actuator 14 f in the axialdirection thereof. Further, a mixing portion 14 d for mixing therefrigerant flowing in from the intake portion 14 c with the refrigerantejected from the nozzle portion 14 a and a diffuser portion 14 b forincreasing the pressure of the refrigerant by increasing the refrigerantpath area gradually are arranged downstream of the nozzle portion 14 a.

The refrigerant that has flowed out of the diffuser portion 14 b of theejector 14 flows into the first evaporator 15 arranged in the air pathof the compartment climate control unit to cool the vehiclecompartments.

Specifically, the compartment climate control air is blown into thefirst evaporator 15 by an electric fan 26 of the compartment climatecontrol unit and the low-pressure refrigerant decompressed by theejector 14 absorbs heat from the compartment climate control air in thefirst evaporator 15. In this way, the compartment air climate controlair is cooled to exhibit the cooling ability. The gas-phase refrigerantevaporated in the first evaporator 15 is sucked into the compressor 12and circulates through the refrigerant circulation path 11 again.

This refrigeration cycle branches from a point between the radiator 13and the ejector 14 in the refrigerant circulation path 11 and forms afirst branch path 16 by merging with the refrigerant circulation path 11at the intake portion 14 c of the ejector 14.

The first branch path 16 includes a first flow rate regulation valve 17for adjusting the refrigerant flow rate and decompressing therefrigerant. The valve opening degree of the first flow rate regulationvalve 17 can be electrically regulated. The second evaporator 18 isarranged downstream of the first flow rate regulation valve 17 in therefrigerant flow.

The second evaporator 18 is arranged, for example, in the on-vehiclecool bag to perform a cooling operation of the cool bag. The air in thecool bag is blown to the second evaporator 18 by the electric fan 27.

The electromagnetic pressure control unit 12 a of the variabledisplacement refrigerant compressor 12, the first blower 26, the secondblower 27 and the first flow rate regulation valve 17 are electricallycontrolled by the control signal from the ECU 25.

Next, the structure and method for fixing the pipe on the ejector areexplained as an example. FIG. 3 is a sectional view showing the statebefore pressure application in the pipe fixing method according to thisembodiment.

First, the pipe 2 has a thin portion 2 a on the inner periphery at anend thereof to be connected with the ejector 1 as an example of theobject member. The thin portion 2 a is formed over the whole round ofthe inner surface of the pipe 2 and constitutes the thinnest portionnormally about ⅔ of the pipe thickness. The shape of the thin portion 2a along the pipe axis is not specifically limited. In the case where thepipe size is reduced progressively radially outward, however, the firstprojection can be advantageously formed.

The thin portion 2 a is formed by cutting the inner periphery of thepipe 2. For example, the pipe 2, while being kept in the same position,is turned in lathe (not shown) and the cutting tool (not shown) appliedto the inner periphery of the rotating pipe 2 is fed centrifugally bythe desired amount of cut. In this way, the thin portion 2 a can beformed on the inner periphery of the pipe 2 by a simple machiningprocess.

A through hole communicating with the path 1 d substantially at rightangles to the axial direction of the ejector 1 is formed on the outersurface of the ejector 1 as an example of the object member. Thisthrough hole is formed with a stopper wall 1 b, an enlarged diameterportion 1 a and a stopper wall 1 c in that order from the side near theouter surface.

The bore of the stopper wall 1 b is set to substantially the same sizeas the outer diameter of the fixed pipe 2 and formed in such a mannerthat the pipe 2 can be inserted through. The enlarged diameter portion 1a is formed with the bore thereof continuously increased from thestopper wall 1 b. The bore of the enlarged diameter portion 1 a isformed to such a size that when the thin portion 2 a of the pipe 2 isdeformed by plastic flow, as described later, the first projection is inclose contact.

The stopper wall 1 c is a tubular wall parallel with the axial directionof the ejector 1 and formed in such a manner as to connect a boreportion formed in the same size as the outer diameter of the pipe 2 fromthe enlarged diameter portion 1 a toward the stopper wall 1 c and a boreportion smaller than the outer diameter of the pipe 2. The pipe 2inserted into the through hole of the ejector 1, with the forward endsurface 2 b thereof in contact with the stopper wall 1 c, is set inposition with the axial motion thereof restricted along the pipe axis.The radial position of the pipe, on the other hand, is limited and setin position by the bore of the stopper-wall 1 b and the bore portionextended toward from the enlarged diameter portion 1 a toward thestopper wall 1 c and formed in the same size as the outer diameter ofthe pipe 2.

This through hole, like the thin portion 2 a of the pipe 2, is formed bycutting. As an example, the ejector 1 is turned with the axis of thethrough hole as a center in the lathe (not shown) while the cutting tool(not shown) applied to the inner periphery of the through hole of therotating ejector 1 is fed inward along the axis of the ejector by anappropriate amount thereby to form the stopper wall 1 b, the enlargeddiameter portion 1 a and the stopper wall 1 c. Thus, the enlargeddiameter portion 1 a can be formed on the ejector 1 constituting theobject member by a simple machining process. According to thisembodiment, the outer diameter of the pipe 2 is 6 to 10 mm and the tubethickness of the ejector 1 is about 5 mm.

The pipe 2 is formed of a metal such as aluminum, aluminum alloy, copperor copper alloy, which is a material adapted to flow plastically underan external force. The object member, on the other hand, is formed of ametal such as aluminum, aluminum alloy, copper, copper alloy, iron,stainless steel or brass, which may be either the same material as, or amaterial different from, the pipe 2 with which it is combined.

The support member 4 is inserted into the path 1 d in the ejector 1having this configuration thereby to support the inner peripheralportion of the ejector 1 while at the same time fixing the ejector 1.Also, the support member 5 is inserted into the pipe 2 to support theinner peripheral portion thereof and, with the axis set coincident withthe center line of the through hole of the ejector 1, fixed by the chuck3. The chuck 3 and the pipe 2 are arranged movably together downward inaxial direction by a press, not shown, for driving the chuck 3.

As shown in FIG. 4, the pipe can alternatively be fixed in the axialdirection of the object member. FIG. 4 is a sectional view showing thestate before pressure is applied to fix the pipe in the axial directionof the object member. In this case, as in the ejector 1 described above,a through hole is formed communicating from an axial end of the objectmember 8 to the flow path 8 d. Thus, the stopper wall 8 b, the enlargeddiameter portion 8 a and the stopper wall 8 c are formed in that orderfrom one end surface of the object member 8.

Next, an explanation is given about the process of pressing the pipe 2against the ejector 1 in the axial direction of the pipe 2. FIG. 5 showsa sectional view showing the state in which the pipe is inserted intothe object member from the state before being fixed shown in FIG. 3.FIG. 6 is a sectional view showing the state after the first projectionis formed from the state of FIG. 5.

As shown in FIG. 5, the chuck 3 is moved axially downward of the pipe 2by a press, and the pipe 2 is advanced into the through hole until theforward end thereof comes into contact with the stopper wall 1 c. In theprocess, the thin portion 2 a is located at a corresponding positionradially inward of the enlarged diameter portion 1 a of the ejector 1.Also, a distance of about 3 mm is secured between the chuck 3 side outerperipheral surface of the ejector 1 and the lower end surface of thechuck 3.

As shown in FIG. 6, pressure continues to be applied by the press tomove the chuck 3 further axially downward of the pipe 2. Then, a plasticflow of material occurs in the thin portion 2 a of the pipe 2, so thatthin portion 2 a moves radially outward of the pipe 2 and is deformeduntil it comes into close contact with the enlarged diameter portion 1 athereby to form the first projection 6 (first buckling step).

In the process, the cross section of the enlarged diameter portion 1 ais formed in the shape progressively reduced in thickness outward alongthe axial direction of the pipe 2. Thus, the deformation of the thinportion 2 a due to the plastic flow is further promoted, while at thesame time improving the closeness between the enlarged diameter portion1 a and the outer surface of the thin portion 2 a. Also, the supportmember 5 inserted in the pipe 2 prevents the deformation of the portionother than the thin portion 2 a of the pipe 2, so that the flow pathspace in the pipe 2 is appropriately maintained, while at the same timepromoting the deformation of the thin portion 2 a radially outward.

By forming the first projection 6 in this way, the stopper wall 1 bexpanded radially inward of the pipe 2 restricts the upward movement ofthe first projection 6 and the pipe 2 is prevented from coming off andis fixed on the ejector 1.

Further, in order to improve the fixing force, a second projection 7shown in FIG. 7 is desirably formed. FIG. 7 is a sectional view showinga state in which the second projection 7 is formed further from thestate shown in FIG. 6. FIG. 8 is a perspective view showing the secondprojection 7. After the first buckling process described above, pressureis exerted from the pipe 2 increasingly against the ejector 1 by thepress. Then, the pipe 2 succumbs to the force of the press and begins tobuckle, so that the outer peripheral portion of the pipe 2 is projectedradially outward in the boundary between the pipe 2 and the chuck 3 sideouter surface of the ejector 1 thereby to form the second projection 7(second buckling process).

Then, the pressure of the press is released and so is the force of thechuck 3 to grip the pipe 2, while at the same time pulling off thesupport member 5 from the pipe 2 and the support member 4 from theejector 1. As shown in FIG. 8, the pipe 2 extending in the directionsubstantially perpendicular to the axis of the ejector 1 is fixed on theouter peripheral surface of the ejector 1. The second projection 7 isformed in a circle in such a manner as to surround the outer peripheryof the pipe 2 in the boundary with the ejector 1 and integrated with theouter surface of the ejector 1.

In this way, the second projection 7 is integrated with the ejector 1and formed in such a manner as to expand radially outward of the pipe 2,and therefore the fixing force of the pipe 2 on the ejector 1 is furtherincreased.

According to this embodiment, the pressure imparted by the press untilthe first projection 6 is formed is, for example, not more than 9.8×10³N and, after the first projection 6 is formed, the pressure of about 1.9to 4.0×10⁴ N is imparted by the press to form the second projection 7.Also, even in the case where a force is applied to press the pipe 2against the ejector 1, the support member 4 inserted in the ejector 1prevents the deformation of the ejector 1. In spite of the larger forcewhich may be exerted by the press, therefore, the appropriate path 1 dcan be secured.

In the case where a curved pipe is fixed on the object member, pressureis applied through the pipe 2 to the ejector 1 making up the objectmember with the support member 5 inserted in the pipe 2 as describedabove. After thus buckling the pipe 2 in the first buckling process orafter the second buckling process to improve the strength further, thesupport member 5 is pulled off from the pipe 2 thereby to form the pipe2 into the desired curved shape. By executing these steps, a curved pipecan be fixed on the object member.

As described above, according to this embodiment, the enlarged diameterportion 1 a which is larger than the outer diameter of the pipe 2 andthrough which the pipe 2 can be inserted along the axial direction isformed in the ejector (object member) 1, the thin portion 2 a is formedon the inner periphery of the pipe 2, and the first projection 6 isformed by the plastic deformation of the thin portion 2 a by thepressure applied to the pipe 2 in axial direction into coincidence withthe large diameter portion 1 a thereby to form a pipe fixing structure.

With this configuration, the enlarged diameter portion 1 a is formed inthe object member and the thin portion 2 a is formed in the pipe 2,after which the pipe 2 is buckled and fixed on the object member. Inthis way, a simple fixing structure having a positive fixing force isrealized.

Also, a pipe fixing structure is desirable in which the secondprojection 7 projected from the outer periphery of the pipe 2 andintegrated with the ejector (object member) 1 is formed in the boundarybetween the pipe 2 and the outer surface of the ejector (object member)1 fixed to each other. In the case where this configuration is employed,the second projection 7 is integrated with the ejector (object member) 1and expanded radially outward thereby to further increase the fixingforce between the pipe 2 and the object member 1.

Also, the cross section of the enlarged diameter portion 1 a in theaxial direction of the pipe 2 desirably assumes a tapered shapeprogressively smaller radially outward of the pipe 2. In the case wherethis configuration is employed, the first projection 6 of the pipe 2plastically flows into close contact in the tapered shape of the crosssection of the enlarged diameter portion 1 a, thereby reducing the gapbetween the object member and the pipe for an improved closeness and ahigher fixing force.

The pipe fixing method according to this embodiment comprises the stepsof forming the thin portion 2 a on the inner periphery of the pipe 2,forming the enlarged diameter portion 1 a, through which the pipe 2 canbe inserted in axial direction, in the ejector (object member) 1 at aposition corresponding to the thin portion 2 a to which the pipe 2 isfixed, and applying the pressure in axial direction by inserting thepipe 2 into the ejector (object member) 1 thereby to project and deformthe thin portion 2 a outward into coincidence with the enlarged diameterportion 1 a.

With this fixing method, after the comparatively simple process offorming the thin portion 2 a of the pipe 2 and the enlarged diameterportion 1 a on the ejector (object member) 1, the pipe 2 is buckled bybeing pressed in axial direction. Thus, a pipe fixing method is obtainedin which the workability, the quality of the buckling process and thefixing force are high.

Also, in the pipe fixing method according to this embodiment, theprocess is desirably executed in which the thin portion 2 a is deformedby plastic flow into coincidence with the enlarged diameter portion 1 a,immediately after which pressure is exerted on the pipe 2 thereby tobuckle the pipe 2 in the boundary between the fixed pipe 2 and the outersurface of the ejector (object member) 1.

By employing this fixing method, the second projection 7 expandedoutward is formed by buckling the pipe 2 in the boundary between thefixed pipe 2 and the outer surface of the object member, with the resultthe fixing force between the pipe 2 and the ejector (object member) 1can be further increased.

Also, the pipe fixing method according to this embodiment desirablyincludes the step of pressing the pipe 2 against the ejector (objectmember) 1 thereby to deform the thin portion 2 a with the support member5 inserted in the pipe 2. By employing this fixing method, the tendencyof the pipe 2 to expand outward during the plastic flow is strengthened,and therefore the chance of obtaining the desired shape can be furtherenhanced by the deformation of the pipe 2.

Also, the pipework 8 side end surface of the chuck 3 shown in FIG. 4 togrip the pipe 2 is formed along the shape of the outer surface of thepipework 8. With this configuration, the second projection can beformed, less visibly, to the desired thickness in the boundary betweenthe pipe 2 and the outer surface of the pipework 8 in the bucklingprocess.

Second Embodiment

This embodiment, as compared with the method of fixing the pipe on theejector according to the first embodiment, represents a fixing method inwhich the pipe 11 having no thin portion is inserted into the ejector 1and set in position, while pressure is applied only on the pipe 11 todeform the pipe 11. FIG. 9 is a sectional view showing the state beforepressing the pipe 11 in the pipe fixing method according to thisembodiment. FIG. 10 is a sectional view showing the state after formingthe first projection from the state of FIG. 9.

As shown in FIG. 9, the pipe 11, like the pipe 2 according to the firstembodiment, is formed of a material adapted for plastic flow under atleast a predetermined external force but has no thin portion 2 a unlikethe pipe 2. The ejector 1, like in the first embodiment, has a throughhole communicating with the path 1 d in the direction substantially atright angles to the axial direction. The through hole is formed,sequentially in the order from the outer surface of the pipe 2, with aninsertion opening, a stopper wall 1 b, an enlarged diameter portion 1 aand a stopper wall 1 c. The stopper wall 1 b, the enlarged diameterportion 1 a and the stopper wall 1 c have the same shape and functionand are processed in the same manner as in the first embodiment.

The support member 12 is inserted into the path 1 d of the ejector 1configured as described above thereby to support the inner peripheralportion of the ejector 1 while at the same time fixing the ejector 1.The support member 12 has an insertion hole through which the support ofa pressure punch member 10 described later can be inserted.

The pipe 2 is arranged on the ejector 1 by inserting the pipe 2 into thethrough hole from the insertion opening on the outer surface of theejector 1 and pushed in until the lower end of the pipe 2 comes intocontact with the stopper wall 1 c. On the other hand, the support of thepressure punch member 10 is inserted into the pipe 2 to support theinner peripheral portion of the pipe 2 by the support of the pressurepunch member, while at the same time arranging the axis of the pipe 2 inalignment with the center line of the through hole of the ejector 1.

The pressure punch member 10 has in the upper part thereof a punchportion larger in outer diameter than the support for supporting theinner peripheral portion of the pipe 2. The pressure punch member 10,under its own weight, causes the lower end portion 10 a of the punchportion thereof to come into contact with the upper end portion of thepipe 2 and thus is integrated with the pipe 2.

Also, the outer surface of the pipe 2 is held in such a manner that theradial motion of the pipe 2 is restricted by a guide member 9 while thepipe 2 can be movable in axial direction. Next, the pipe 2 thus set inposition is buckled under the pressure applied thereto by the punchportion of the pressure punch member 10. The punch portion of thepressure punch member 10 is pressed downward by the press machine sothat the lower end 10 a of the punch portion pushes the upper end of thepipe 2 axially downward.

Upon application of at least a predetermined external force to thepressure punch member 10, the tissue of the pipe 2 begins to flowplastically. As shown in FIG. 10, the plastic flow occurs in the spaceformed between the inner surface of the enlarged diameter portion 1 aand the outer peripheral surface of the pipe 2. The radially insideportion of this space in which the plastic flow occurs is supported bythe support of the pressure punch member 10, and therefore the plasticflow occurs radially outward to fill the space. Thus, the pipe 2 isprojected outward and deformed into coincidence with the enlargeddiameter portion 1 a.

As described above, the pipe fixing method according to this embodimentcomprises the step of forming an opening of the ejector (object member)1 into which the pipe 2 can be inserted and forming the enlargeddiameter portion 1 a larger than the insertion opening and the outersize of the pipe 2 in the ejector 1, and the step of inserting the pipe2 into the ejector 1 by way of the insertion opening and pressing onlythe pipe 2 in axial direction with the outer surface of the pipe 2supported, thereby projecting the outer peripheral portion of the pipe 2outward into coincidence with the enlarged diameter portion la.

In the case where this pipe fixing method is employed, a more simplefixing method is realized in which the process of shaping the ejector 1to conform to the outward projection is eliminated.

Third Embodiment

In the third embodiment, as compared with the method of fixing a pipe onan ejector according to the first embodiment, a fixing method and afixing structure capable of forming the second projection into thedesired shape are explained. FIG. 11 is a sectional view showing thestate before forming the second projection in the pipe fixing structureand method according to this embodiment. FIG. 12 is a sectional viewshowing the state after the second projection is formed from the stateshown in FIG. 11.

The pipe fixing method according to this embodiment has the same stepsas the pipe fixing method according to the first embodiment up to thefirst buckling step, i.e. the step of forming the first projection 6 bydeforming the thin portion 2 a into coincidence with the enlargeddiameter portion 1 a.

According to this embodiment, the ejector 1 side end surface 14 of thechuck 13 for gripping and moving the pipe 2 in axial direction is formedin the shape following the outer surface of the ejector 1. Also, the endsurface 14 of the chuck 13 is preferably formed as a slope or a curvefollowing the curved shape of the outer surface of the ejector 1.

The process of pressing the pipe 2 against the ejector 1 in axialdirection using this chuck 13 is explained. First, the distance of atleast about 3 mm is secured between the chuck 13 side outer peripheralsurface of the ejector 1 and the lower end surface of the chuck 13, andthe pipe 2 is fixed by the chuck 13. The chuck 13 is moved axiallydownward of the pipe 2 by a press, and the pipe 2 is advanced into thethrough hole of the ejector 1 until the forward end of the pipe 2 comesinto contact with the stopper wall 1 c. In the process, the thin portion2 a of the pipe 2 is located at a position corresponding radially inwardto the enlarged diameter portion 1 a formed on the ejector 1.

Further, pressure continues to be applied to the chuck 13 by the pressto move the chuck 13 axially downward of the pipe 2. Then, as shown inFIG. 11, the plastic flow of the issue occurs in the thin portion 2 a ofthe pipe 2, and the thin portion 2 a is moved radially outward of thepipe 2 and deformed until it comes into close contact with the enlargeddiameter portion 1 a, thereby forming the first projection 6 (firstbuckling step).

Next, the process of forming the second projection 15 shown in FIG. 12is explained. After the first buckling step described above, the chuck13 is moved axially further downward by the press to increase thepressure applied to the ejector 1 through the pipe 2. Then, the pipe 2,no longer able to bear the force of the press, begins to buckle and theouter peripheral portion of the pipe 2 begins to be projected radiallyoutward in the boundary between the chuck 13 side outer surface of theejector 1 and the pipe 2.

The outer peripheral portion of the pipe 2 that begins to project iscrushed by the end surface 14 of the chuck 13, and the pipe portionprojected outward by the plastic flow spreads following the curved shapeof the outer surface of the ejector 1, thereby forming the secondprojection 15 of uniform thickness (second buckling step).

As described above, the second projection 15 in the pipe fixingstructure according to this embodiment is formed with a substantiallyuniform thickness along the shape of the outer surface of the ejector 1.This configuration makes less visible the coupling in the boundarybetween the pipe 2 and the outer surface of the ejector 2 while at thesame time reducing the size of the generated burrs.

Also, that end surface 14 on the side of the chuck 13 used in the pipefixing method according to this embodiment which grips the pipe 2 andwhich is in opposed relation to the outer surface of the ejector 1 isformed along the shape of the outer surface of the ejector 1. Thisconfiguration reduces the size of the burrs in the boundary between thepipe 2 and the outer surface of the ejector 1 on the one hand and thesecond buckling portion 15 can be formed to the desired thickness on theother hand.

While the invention has been described by reference to specificembodiments chosen for purposes of illustration, it should be apparentthat numerous modifications could be made thereto, by those skilled inthe art, without departing from the basic concept and scope of theinvention.

1. A pipe fixing structure for deforming and fixing a pipe by applying aforce to press the pipe in axial direction against an object member towhich the pipe is to be fixed, the pipe fixing structure comprising: anenlarged diameter portion formed in the object member, which portion islarger than the outer diameter of the pipe and through which the pipecan be inserted in axial direction; and a first projection into theshape of which a thin portion of the pipe is deformed under thepressure; wherein the first projection coincides with the enlargeddiameter portion.
 2. A pipe fixing structure according to claim 1,comprising a second projection projected radially outward from the pipeand integrated with the object member in the boundary between the fixedpipe and the outer surface of the object member.
 3. A pipe fixingstructure according to claim 2, wherein the second projection is formedin a substantially uniform thickness along the shape of the outersurface of the object member.
 4. A pipe fixing structure according toclaim 1, wherein the cross section of the enlarged diameter portion inaxial direction of the pipe is progressively reduced outward.
 5. A pipefixing structure according to claim 1, wherein the object member is anejector for the refrigeration cycle.
 6. A pipe fixing method comprisingthe steps of: forming a thin portion on the inner periphery of the pipe;forming an enlarged diameter portion, in the object member to which thepipe is fixed, which portion is located at a position corresponding tothe thin portion and through which the pipe can be axially inserted; andinserting the pipe into the object member, and pressing the pipe inaxial direction so that the thin portion is deformed by being projectedoutward into coincidence with the enlarged diameter portion.
 7. A pipefixing method according to claim 6, wherein the pipe inserted into theobject member is pressed in axial direction by gripping the outerperipheral portion of the pipe with a chuck and moving the chuck inaxial direction.
 8. A pipe fixing method according to claim 6, whereinthe thin portion is deformed into coincidence with the enlarged diameterportion, after which pressure is applied to the pipe thereby to bucklethe pipe in the boundary between the fixed pipe and the outer surface ofthe object member.
 9. A pipe fixing method according to claim 8, whereinthe chuck moved in axial direction while gripping the outer peripheralportion of the pipe has an end surface in opposed relation to the outersurface of the object member on the side thereof for gripping the pipe,which end surface is formed along the outer surface of the objectmember.
 10. A pipe fixing method according to claim 9, wherein the outersurface of the object member is curved, and that end surface of thechuck which grips the pipe and which is nearer to the object member iscurved or inclined along the shape of the curved outer surface of theobject member.
 11. A pipe fixing method according to claim 6, comprisingthe step of inserting the pipe into the object member and pressing theobject member in axial direction with a support member inserted in thepipe, thereby deforming the thin portion into an outward projectioncoincident with the enlarged diameter portion.
 12. A pipe fixing methodcomprising: the step of forming an opening into which the pipe can beinserted, in the object member to which the pipe is to be fixed, andforming an enlarged diameter portion larger than the insertion openingand the outer size of the pipe in the object member; and the step ofinserting the pipe into the object member from the insertion opening andholding the outer surface of the pipe while deforming by projecting theouter peripheral portion of the pipe outward into coincidence with theenlarged diameter portion by applying the axial pressure to only thepipe.